The present invention relates to a shank for a milling tool, preferably an end mill. The invention also relates to a coupling arrangement between a shank for a milling tool and a chuck.
Rotating tool shanks of cylindrical shape can be clamped in holders of different types, e.g., Weldon-chucks and Whistlenotch-chucks. In these chucks the axial locking and the rotational driving are special for each type of holder. Examples of standard types of a Weldon-chuck and a Whistlenotch-chuck will be given below.
The prior art device shown in FIG. 1 includes a standard chuck 10 of Weldon type and a prior art standard shank 11 that is received in an axial boring 12 of the chuck 10. A first locking screw 13 and a second locking screw 14 are arranged in mating first and second radial borings 15 and 16 in the chuck 10, the radial borings 15 and 16 having a longitudinal extension (axis) generally transverse to the longitudinal center axis 17 of the boring 12. The longitudinal center axis 17 is also the longitudinal center axis of the chuck 10 and the shank 11 when the shank 11 is mounted in the boring 12 of the chuck 10.
The locking screws 13 and 14 are externally threaded while the radial borings 15 and 16 are internally threaded. When rotating the locking screws 13 and 14 they are displaced in the radial direction of the chuck 10 either inwardly or outwardly depending upon the direction of rotation of the locking screws 13 and 14.
The shank 11 is provided with two recesses 18 and 19 having a certain extension both radially and axially. The recesses 18 and 19 are designed to cooperate with the locking screws 13 and 14.
Before clamping the shank 11 in the boring 12 of the chuck 10 it is checked that the locking screws 13 and 14 are in a position to allow the shank 11 to be inserted in the boring 12. After the shank 11 is inserted in the boring 12 to a predetermined extent the locking screws 13 and 14 are displaced radially inwardly by rotating the locking screws 13 and 14 in a predetermined direction. As is indicated in FIG. 1 the first locking screw 13 is in its active position cooperating with the recess 18 and exerting forces upon the shank 11 that will lock the shank 11 in the axial direction. It is also indicated in FIG. 1 that the second locking screw 14 in its active position cooperates with the recess 19 and exerts a force upon the shank that will prevent the shank 11 from rotating relative to the chuck 10.
The prior art device in FIG. 2 shows a standard chuck 20 of Whistlenotch type and a prior art standard shank 21 that is received in an axial boring 22 of the chuck 20. A locking screw 23 is received in a radial boring 24 of the chuck 20. The screw 23 is externally threaded while the radial boring 24 is internally threaded. The longitudinal axis of the locking screw 23 has an extension (axis) transverse to the longitudinal center axis 25 of the axial boring 22. The longitudinal center axis 25 is also the longitudinal center axis of the chuck 20 and the shank 21 when the shank 21 is mounted in the axial boring 22. However, the longitudinal axis of the locking screw 23 is not perpendicular to the longitudinal center axis 25 of the chuck 20 but rather is angled 2.degree. from perpendicular, i.e., 2.degree. relative a radius of the shank, to exert an axial force upon the shank 21 that is directed towards the bottom of the axial boring 22.
The shank 21 has a planar recess 26 that runs generally in the longitudinal direction of the shank 21, the planar recess being angled relative to the longitudinal axis of the shank 21. By cooperation of the locking screw 23 and the recess 26 the shank 21 will be forced towards the bottom of the axial boring 22. This means that the screw 23 locks the shank 21 against axial outward displacement and simultaneously against rotation around its longitudinal center axis 25 relative to the chuck 20.
The prior art holders for cylindrical tool shanks described above are not stabilized to a sufficient degree. The present invention deals with designing the tool shank in such a way that an increased stability is achieved also when using standard holders, e.g., prior art Weldon-chucks and Whistlenotch-chucks.